This blog provides updated forecasts and comments on current weather or other topics

Saturday, January 14, 2012

3 PM Snow Nowcast

It was an exciting morning...with some wet snow hitting a number of places as the front moved through and the convergence zone formed in its wake. In fact, it is snowing NOW in the CZ near Everett!

The interesting thing is that the air was still relatively warm this morning and afternoon, but evaporation and melting drove the snow and freezing levels down--particularly where intensity was great. A great example of this can be seen at the UW, where the intense precipitation with the front and following CZ cooled the temperatures down quickly (see graphic, third panel down is temperature (black) and dewpoint (red))

As the precipitation ended near Seattle and elsewher, the temperatures have warmed up and now (according to Snowwatch) the freezing level is around 1500 ft outside of precipitation (see below). Remember, that implies a SNOW LEVEL of around 500 ft.

The greatest convergence zone precip around noon was north of Seattle. Look at these surface temps at that time--WAY cooler north of the city where the precip was heavier.

Here is the latest radar image...you can see the convergence zone precip (including snow) over the north Sound and the showers coming in off the ocean (thanks to the new radar!). Snow showers in the mountains.

These showers will continue to move in, and the convergence zone should bring snow to the north Sound for several more hours. Here is a traffic cam near Everett...really snowing there now.

A bigger general snow threat is tomorrow when an upper trough moves in and revs ups the precipitation, with an associated low center moving into the region. It will be much colder then and a few inches of snow could result over Seattle and NW Washington.

Then another disturbance moves in late Monday (more snow!) and then on early Wednesday we could a lot of wet snow as a warmer disturbance moves in, eventually leading to rain. But more on that later.

30 comments:

Thanks for the nowcast. While I was waiting for it, I read your paper. Nice piece of educational outreach for us regular folks in the community who like to see the details from time to time. Observationally, here near echo lake in east king county it has been steadily snowing for the past 4 hours and is now really picking up again. Hope your lost dog has holed up in a warm place.

Wednesday looks to be the big kahuna, if things come together just right. This far out, it looks like the forecasters are a little shy about pulling the trigger - and I don't blame them. We've been down this road before. :)

By the way Cliff, been meaning to thank you for the blog. Really enjoy visiting everyday (even during the summer!). You are part of my daily routine. Totally appreciate the work you put into the site! Keep it up.

Just love the nowcasts! It's really a great learning experience to have your analysis as the weather's actually happening.

West Seattle has had sun and scattered clouds most of the afternoon. Keeping fingers crossed for serious snow in the next few days! (Especially if it happens right before I'm supposed to teach on Tuesday so we can cancel classes...it's not just the kids who want a snow day off!)

Great Nowcast! Thanks. I noticed that as of yesterday you were making some interesting predictions for the late week warm front that the models were predicting. It looked like this could be very active. As a guy who lives on a boat in Lake Union, should I get some extra lines out for that later disturbance? Any help you could be figuring out what will be coming will be appreciated.

PS

You seem to be the only forecaster who caught the big warm front. There was little written about it by the other sites I watch.

I just viewed today's timelapse from the Atmospheric Sciences rooftop camera. Wow! It's one of the most interesting I've seen. Radical shifts in wind direction/cloud movement starting around 11:16 and shifting several times later, along with major changes in cloud cover and sky. I would *love* to get an explanation for what we see in that movie.

The 06z run of the NAM valid 18z Wednesday has a 992mb low coming in to the mouth of the Columbia River 18z Wed. So snow is possible Wednesday. Spin up the low and make it stronger and keep it on the same path, and there is a chance for heavy snow Wednesday in Seattle. It is a day or two too early to sound the alarm on this, and there are a dozen ways to spoil a snow forecast in Seattle, but a deeper low that tracks in just south of Seattle would probably draw cold air into the Seattle area and overrun it. It would likely be sloppy, heavy wet snow, but maybe the models will trend a bit cooler too--I think Monday is the day you would want to make some choices about choosing a model and making some bets. Too early now to say anything with any confidence.

Cliff ~ I would say "confused" is a mild description....Clearly they know nothing about weather in the NW....While it would be awsome to have a foot of snow in Seattle, it would also be a miracle...in one dumping, anyway! I wonder if accuweather ever follows up on their NW/Seattle forcasts? LOL!

THANK HEAVEN for the legacy radar! This morning it showed the CZ right over North Whidbey extending east to Mount Vernon. Sadly used this data to cancel a drive to Darrington towing a boat for a float on the Sauk River. Have ~3" of snow in Oak Harbor.http://radar.weather.gov/radar.php?rid=atx&product=N0R&overlay=11101111&loop=no (time of image 0639 15 Jan)mjgrota returnsThe new radar provided no coverage of this feature.

Thus far this weekend's weather continues to be a non-event up here at the Canadian border. Nothing as predicted, for the most part, which only serves to frustrate those of us who insist on reading weather blogs & such. Once most of the Saturday morning slush cleared away, the remainder of the day was pleasant. Sunday morning is partly sunny, partly cloudy with no wind and fairly mild temps.

Managed to make it into work this morning. Up in the Issaquah highlands there's just a dusting of snow (and I've noticed it's reached all the way down where I work in Seattle near the Space Needle).

However, on my way to work heading West on the I-90, I noticed the snow showers are progressively getting heavier. I may not be staying here long if it gets worse where I live. I'd like to make it home in one piece before conditions get icy. Enjoying the flurries though! They were huge by the time I got on the I-5 North connector. :)

W00t! I'm certainly hoping for a few inches.

As for the Accuweather guy. It's obvious he's a few cards short of a full deck. The fact that he's reporting from the East coast just supports the fact that in addition to not being a local, he is using overzealous terminology to describe the snow. (I think he's just using that as a ploy to draw attention). This is not Snowmageddon and he lacks the understanding one must have in regards to the unique weather conditions of the NorthWest. I found his glowing report to be utterly amusing in its glaring naiveté.

Close to five inches this morning in the Seattle Hill/Silver Firs area of South Snohomish County (elev. 450'), as convergence has formed again this morning. Shows no signs of stopping. Decided to cancel today's skiing plans and just stay home and enjoy this treat! It's beautiful! Hope it keeps coming!